This invention relates to the field of computer disk drives, and more particularly to a method for attaching a slider to a suspension in a controlled manner that provides consistent bonding characteristics between the slider and suspension thus improving performnance of the disk drive.
Magnetic disk drives typically utilize one or more disks mounted to a rotatable hub. The hub in turn is connected to a spindle motor which can rotate the disk at speeds in excess of 7,000 revolutions per minute. Read/write heads, or transducers, are positioned relative to tracks on the disks for reading data from and writing data to the disks. The read/write heads are positioned by rotary actuator arm assemblies. A rotary actuator arm assembly typically comprises an actuator arm, a suspension arm or load beam, and a slider. The actuator arm is attached to a spindle and rotates by action of a voice coil motor. The suspension arm or load beam is attached to the actuator arm. The slider is then attached to the free distal end of the suspension arm. The suspension arm biases the slider toward the surface of the disk. A read/write head or transducer is fixed to the slider. The transducer is typically adhered to the trailing end of the slider, but may be affixed at other locations on the slider body. Sliders are designed to either fly just above the surface of the disk or to actually contact the disk as it rotates. In order to maintain consistent flight characteristics, it is important that each slider be mounted to its corresponding suspension arm in an accurate and consistent manner. Inconsistent mounting of the slider can affect the aerodynamics of the slider, causing it to be misaligned relative to the tracks on the disk. Such misalignment can cause read/write errors, and can otherwise negatively affect disk drive performance.
Adhesive is used to attach the slider to the suspension arm. Previously, there have been inadequate control measures adopted to positively control the amount of adhesive applied, or to control the exact locations where adhesive is applied. As a result, sliders are bonded to the suspension arms in an inconsistent manner which ultimately affects the performance of the slider. For example, after adhesive has been applied, the adhesive must be cured which involves heat drying of the slider and suspension arm. Typically, the slider is made of a ceramic material and the suspension arm is metallic. Accordingly, these components expand and contract at different rates in response to the heated drying. If the adhesive is not placed at consistent locations in consistent amounts, the expansion and contraction which takes place in the heated drying process causes inconsistent forces being applied to the slider, resulting in twisting, crowning and/or cambering of the slider. Thus, sliders will be inconsistently mounted to suspension arms and will perform inconsistently. This will result in potential read/write errors and other associated problems among disk drives and even among head assemblies within a single disk drive.
Another problem associated with prior art methods of attaching a slider to a suspension arm is that the type of adhesive used is not conducive to allow reworking of the device. More specifically, previous adhesives use permanent bonding agents which create a permanent bond between the suspension arm and the slider. Therefore, should either the transducer or the suspension assembly fail in testing, it is necessary to replace the entire suspension assembly rather than separating the two components and reusing the satisfactory component.
Finally, static build up in the head assembly is a common problem with all disk drives. Excessive static build up in the suspension transferred to the disk can result in corruption of data in the disk tracks, as well as actual damage to the disk tracks themselves, which manufacturers seek to create a conductive path from the head assembly through the actuator assembly to ground any static build up, improved methods of dissipating electrostatic build up are always sought.
The present invention solves the foregoing problems by providing a method for attaching a slider to a suspension arm in a consistent, controlled and reliable manner. Polyimide walls are positioned to form a perimeter adhesive zone or area on the attachment surface of the gimbaled flexure or gimbal. The gimbal is the portion of the suspension arm which attaches to the slider. The space inside the walls is filled with adhesive which becomes active upon heating. The slider is then brought in contact with the gimbal of the suspension arm. The suspension arm and slider are subsequently heated to cause the adhesive to turn to a flowable state. Removing the heat causes the adhesive to solidify and adhere the slider to the gimbal. However, because the slider is ceramic and the gimbal is metal, they expand and contract at different rates. This results in different forces applied to the slider, causing unpredictable twisting, crowning and cambering of the slider. The polyimide walls ensure a controlled placement of an adhesive zone and, thereby, consistent placement of the adhesive and of the slider relative to the suspension arm. An opening formed in the wall creates a break or gap allowing excess adhesive to flow out of the bonding area. The excess flows in a controlled manner without contacting other parts of the components thus maintaining a consistent bonding area.
In order to improve reworkability of the disk drive, and particularly the connection between the slider and suspension arm, the adhesive used may be a reworkable solder paste. Upon reheating, the solder paste would melt, thus allowing easy removal of the slider from the suspension. Another material which can be used to improve reworkability is a thermal plastic adhesive which would become liquid upon reheating.
In order to help create a sufficient bond between the slider and the suspension, the surface of the slider which attaches to the suspension could be provided with a metallic film which would be placed in alignment for contact with the adhesive zone. This metallic film may be applied to the slider by sputtering or other deposition processes. Another advantage of employing the metallic film on the slider is to provide a conductive path for removing static from the head/transducer. Accordingly, static can be. dissipated through the metallic film on the slider, through the solder paste, or any other conductive adhesive, and through the suspension arm and actuator arm until it is grounded in the housing of the disk drive.
The present method of attachment further is conducive to an automated assembly. The reservoir or pocket created by the polyimide walls creates a consistent location for adhesive placement and the opening in the wall allows excess adhesives to be utilized without detriment. In turn, a consistent, reliable and stronger bond is created between the slider and suspension arm. Automation enhances the output of the assembly process.